1. Field of the Invention
The present invention relates to a bearing adapter assembly for a railcar truck. More specifically, tightly secured bearing adapters firmly hold the axle bearing in position to avoid angling and lateral axle variation, and the resultant truck "warping". Past research has illustrated railcar truck warping induces truck hunting during railcar travel, which warping causes undue wear on rails and wheels as well as increasing fuel usage.
2. Description of the Prior Art
In a three-piece railcar truck assembly, the side frames and bolster are generally square, that is the axles and bolster are approximately parallel to each other, and the side frames are parallel to each other but normal to the axles and bolster. After truck assembly and at certain railcar speeds, the truck may become dynamically unstable, which may be loosely defined as truck hunting. Truck hunting is defined in the Car and Locomotive Cyclopedia (1974) as "an instability at high speed of a wheel set (truck), causing it to weave down the track, usually with the (wheel) flanges striking the rail." Truck hunting has been the subject of many past and ongoing research efforts within the rail industry by truck suppliers, car builders and railroad lines, as this condition is undesirable from both operational and safety considerations. Past research efforts have noted a significant relationship between truck warping and resultant truck hunting. These research efforts and some of their conclusions are discussed in the ASME paper, "Truck Hunting in the Three-Piece Freight Car Truck" by V. T. Hawthorne, which paper included historical reference to still earlier research in this field. One of the earlier researchers noted ". . . that in the empty car the higher column force of the constant column damping provides a greater warp stiffness and, consequently, yields a higher critical (truck) hunting speed." The ASME paper described a project that was designed to measure the following parameters: warp stiffness; lateral damping force; and, lateral spring rate.
The warp stiffness results in this Hawthorne project duplicated earlier test results and it was noted that as the warp angle increased to 1.degree. (60 minutes) of angular displacement, the warp stiffness dropped off appreciably. Further, it was noted that earlier warp stiffness data showed that 1.degree. of displacement represented the maximum warp travel of a relatively new truck during hunting. Therefore, at warp angles prevalent in truck hunting, the warp stiffness fell considerably below the values necessary to raise the critical speed of hunting above the normal operating range of the freight railcar.
A field test noted that a new railcar truck running at a speed above 60 miles per hour with track inputs causing warp angles below 0.3.degree. would not be expected to hunt. However, if the warp angle suddenly became 1.0.degree. due to a track irregularity, it is expected that the critical truck hunting speed of the railcar would drop to about 52 miles per hour and intermittent truck hunting would occur.
A three-piece railcar truck generally allows a considerable amount of relative movement between the wheel and axle assembly, or the wheelset which includes the axle, wheels and the bearings, and the supporting side frame at the side-frame pedestal jaw. This may be due to manufacturing tolerances permitted in the various components, that is the side-frame pedestal jaw and bearing adapter, and to the form of the connection for the bearing adapter, the journal end of the wheelset and the integral jaws of the side frame structure. U.S. Pat. No. 3,211,112 to Baker discloses an assembly to damp the relative lateral movement between the wheel and axle assembly, and the associated side frame. More specifically, a resilient means or member is provided between the top of the journal end of the wheel and axle assembly, and the associated side frame member to produce varying frictional forces for damping the relative movement between the assembly and the side frame. The Baker-'112 patent recognized the undesirability of transmitting track perturbations through the wheelset, side frames and bolsters, but inhibition of this force transmission is intended to be accomplished by damping the disturbances caused by the lateral axle movements, not by suppressing their initiation.
In U.S. Pat. No. 3,274,955 to Thomas and also in U.S. Pat. No. 3,276,395 to Heintzel, a roller bearing adapter is illustrated with an elastomer on the upper part of the cap plate, which adapter is positioned in the side frame pedestal jaw with the elastomer between the pedestal roof and the adapter for relieving exposure to high stresses. A similar concept is shown in U.S. Pat. No. 3,381,629 to Jones, which provided an elastomeric material between each bearing assembly and the pedestal roof to accommodate axial movements of the bearing assemblies of each axle and to alleviate lateral impact to the side frame.
Other means have been utilized for maintaining a truck in a square or parallel relationship. In U.S. Pat. No. 4,103,623 -Radwill, friction shoes are provided to frictionally engage both the side frame column and bolster. This friction shoe arrangement is intended to increase the restraining moment, which is expected to result in an increased truck hunting speed. The friction shoes had contact surfaces with some appropriate manufacturing tolerance to control initial contact areas to develop a maximum restraining moment.
U.S. Pat. No. 4,192,240 to Korpics provided a wear liner against the roof of a side-frame pedestal jaw. The disclosure recognized the detrimental effects of having a loose wear liner in the pedestal jaw. Wear liners are provided against the roof of the pedestal jaw to reduce wear in the roof caused by oscillating motions of the side frame relative to the wheel-axle assembly and the bearing. The disclosed wear liner included upwardly projecting tabs to grip the roof and side frame to inhibit longitudinal movement of the wear liner, and downwardly projecting legs to cooperate with the pedestal-jaw stop lugs to inhibit lateral movement of the wear liner relative to the roof. The stop lugs of the pedestal jaw are positioned on opposite sides of the depending legs of the jaw, which lugs are engageable with the downwardly depending wear liner legs.
U.S. Pat. No. 3,621,792 to Lisch provides a pedestal jaw opening with outwardly sloped sidewalls and a bearing adapter with sloped sidewalls positioned in the jaw opening. An elastomeric is positioned between the adapter and the pedestal sidewall and roof, which elastomer provides resistance in compression and yieldability in shear, and sufficient softness for cushioning. It is noted that by positioning the elastomeric pad between all the interfaces of the adapter and the pedestal jaw, metal-to-metal contact is prevented along with wear and transmission of noise and vibration from the track to the truck framing. Similarly in U.S. Pat. Nos. 3,699,897 and 4,416,203 to Sherrick, a resilient pad is provided between the bearing adapter and the side frame.
In U.S. Pat. No. 4,072,112 to Wiebe, an elastomeric positioning means is placed intermediate the bearing carrier and one of the pedestal jaws to bias the bearing carrier into direct communication or engagement with the opposite pedestal jaw to limit relative angular movement and linear displacement of the wheel set to the side frame.
U.S. Pat. Nos. 4,108,080 and 4,030,424 to Garner et al. teach a rigid H-frame truck assembly having resilient journal pads in the pedestal jaws. The truck provided by this development demonstrated improved riding characteristics. Similarly U.S. Pat. Nos. 4,082,043 and 4,103,624 to Hammonds et al. disclose an integral H-frame truck with resilient elements in the journal bearings.
In U.S. Pat. No. 4,242,966 to Holt et al., a railcar truck has a transom with a pair of tubes rigidly connected between the longitudinally extending side frames. The transom allows vertical movement of the side frames but resists longitudinal displacement of the side frames with respect to each other.
U.S. Pat. No. 4,841,875 to Corsten et al. provides a suspension arrangement with at least two annular elastomeric shock absorbers having an optimum adjustability in the longitudinal and transverse directions of the vehicle.
Alternative means for the insertion and securing of a wear liner against a pedestal jaw roof are taught in U.S. Pat. Nos. 4,034,681 and 4,078,501 to Neumann et al. and U.S. Pat. No. 4,192,240 to Korpics, which patents have a common assignee. The objective of these patent disclosures was to provide improved means for securing a wear liner in the jaw to minimize its movement and to improve the assembly means. The wear liners are provided with downwardly depending legs and stop lugs positioned to inhibit movement of the wear liner, such as in the lateral direction relative to the roof.
U.S. Pat. No. 4,428,303 to Tack illustrates a clip-on pedestal wear plate especially adapted for worn pedestal surfaces. A pair of wear plates, or a single member with a central portion of the plate removed, may be used to provide the structure of the invention.
All of the above disclosed apparatus disclose a journal assembly or an assembly for a railcar truck axle end, which assembly is operable in the pedestal jaw, and the disclosures recognized the desirability of keeping the truck side frames aligned with each other to avoid truck hunting. However, the several disclosures provided a plurality of resilient means or structures in the pedestal jaw and around the axle journal bearings, but none of the structures addressed the problem of maintaining the bearing adapter and consequently the axle and side frames in their aligned positions. Several of the above-noted references specifically utilized elastomeric or resilient components in the pedestal jaw or in association with the journal bearing to accommodate the disturbances and flexing motions experienced by the axles and side frames.